But zoos say they've already taken big steps to improve the lives of the elephants in their care.

Miranda Stephenson from the British and Irish Association of Zoos and Aquariums (BIAZA) said: "We're giving them bigger and softer areas, which is better for their feet, we're keeping them in bigger groups and we're keeping mums with their daughters so we've got proper families.

"We're also looking at their diets and making them less fattening."

Animal welfare

The study, carried out by scientists from the RSPCA and Zoological Society of London, looked at 4,500 African and Asian elephants.

They say elephants need more regular health checks, shouldn't be transferred from one zoo to another and that calves should stay with their mums for as long as possible.

Will Travers, from the Born Free wildlife charity, says sometimes we have to think about it from the animals' point of view.

"These reports tell us that elephants are having such a bad time in captivity. Do we really want to put them through that?," he said.

Recommendations

But other people argue that zoos provide an important role in conservation, ensuring that elephants survive for future generations.

Now the people who advise the British government on zoos say they'll be studying the new research before making their latest recommendations for zoos within the next six months.